Unknown: Irritable Bowel Syndrome

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Unknown: Irritable Bowel Syndrome

Causes and Symptoms
The Future
For more information


Irritable bowel syndrome or IBS is a chronic (long-term) disorder of the digestive tract characterized by changes in bowel habits—constipation, diarrhea, or a combination of both—along with abdominal cramps and bloating or gassiness. It is not contagious, inherited, or a forerunner of cancer.


IBS is a functional disorder of the digestive tract, which means that it affects the workings of the digestive system rather than its structure. IBS is a common disorder around the world. People with IBS experience cramping or bloating in the abdomen after a meal followed by an urgent need to defecate. The patient typically notices that the stools are more frequent, looser, and may contain mucus. There are four basic patterns: the patient has mostly diarrhea; the patient is mostly constipated; the constipation alternates with diarrhea; or the patient has a mixture of the two conditions. About 75 percent of patients change from one subtype to another within a year, however.

IBS is a chronic rather than an acute disorder with rapid onset. It does not usually get worse over time and is not accompanied by weight loss, loss of appetite, fever, or blood in the stools. Patients with these symptoms usually have other digestive disorders.

Patients with IBS are likely to have certain other disorders at the same time. These include fibromyalgia, lactose intolerance, food allergies, migraines or other recurrent headaches, depression, and backache.


IBS is common in the general American population, affecting as many as a fifth of the adult population. Only 10 to 20 percent of people with symptoms of IBS consult a doctor, however. Most of those seeking treatment are adults but many report that their symptoms began in childhood. Half of all patients diagnosed with IBS state that their symptoms started before age thirty-five. Patients who are over forty when their symptoms begin are less likely to have IBS and more likely to have another digestive problem.

The gender ratio of IBS varies from country to country. In the United States and Europe, women are two to three times more likely than men to have the disorder, but in India, 70 percent of IBS patients are men. The reasons for this difference are not yet known. Some doctors in the United States think that women are more likely than men to seek help for their symptoms rather than being more likely to develop it.

IBS is thought to be equally common in all racial and ethnic groups in Europe and the United States, although some researchers state that the disorder is less common among Asian Americans.

Causes and Symptoms

The cause of IBS is not known. There are, however, several theories about the possible causes of the disorder. These include:

  • Infections. Some researchers think that IBS may be caused by a bacterial infection. Evidence for this includes signs of inflammation in the small bowel of some patients with IBS as well as the fact that some patients diagnosed with IBS did not have symptoms until they had a gastrointestinal infection.
  • Emotional trauma. Some studies indicate that a significant number of women diagnosed with IBS are survivors of physical or sexual abuse.
  • Abnormal patterns of contraction of the muscles in the walls of the intestines. During the process of digestion, the muscular walls of the intestines push food along the digestive tract by rhythmic contractions. In some patients with IBS, the contractions are too close together or too far apart, leading to the cramping sensations and diarrhea or constipation of IBS.
  • Unusual sensitivity of the nerve endings in the intestines. Some researchers think that the intestinal tissues in patients with IBS are more sensitive to stretching than those in most people, or that there are more intense connections between the central nervous system and the intestines in patients with IBS.

In addition to cramping, bloating, and changes in bowel habits, patients with IBS may have the following symptoms:

  • Feeling a need to defecate even when there is nothing in the bowel or rectum.
  • Feeling that the bowel has not been completely emptied after a movement.
  • Finding that cramps and gassiness are relieved by a bowel movement.
  • Visible swelling or bloating of the abdomen.
  • Finding mucus in the stools.


IBS is a diagnosis of exclusion, which means that the doctor must rule out other possible causes of the symptoms. There is no single laboratory test or imaging study that can confirm a diagnosis of IBS. There are several sets of diagnostic criteria drawn up by various professional groups that the doctor can use. Most of these criteria state that the patients must have had abdominal pain or bloating for at least twelve weeks in the past year; that the pain is relieved by a bowel movement; and that the patient has noticed changes in the shape, frequency, or appearance of the stools.

If the patient is over fifty, the doctor may order tests to rule out the possibility of colon cancer. Other tests may be ordered if the patient has fever, weight loss, blood in the stools, or persistent pain, as these symptoms are not characteristic of IBS.


There is no cure for IBS. Patients may be treated with a combination of medications, dietary adjustments (described more fully in the section on prevention), and psychotherapy. In some cases the doctor may ask the patient to keep a food diary to see whether certain foods make the symptoms worse. Patient education is a very important part of treatment for this disorder, as there are steps that patients can take to manage their symptoms and reduce the frequency of flare-ups.

The specific medications prescribed depend on the patient's most bothersome symptoms. They may include:

  • Fiber supplements like Metamucil or Citrucel. These are taken with fluids to relieve constipation.
  • Antispasmodic drugs. These are given to slow down the contractions of the intestines. They include drugs like Bentyn and Levsin.
  • Antidepressants. Drugs like Paxil and Prozac are reported to help patients with severe constipation. They are also given to IBS patients with coexisting depression.
  • Antidiarrheal medications. Imodium and Lomotil are the drugs most often recommended for treating severe diarrhea.
  • There are also some newer drugs that are available only for patients who do not respond to other treatments. Lotronex and Tegaserod are drugs approved only for temporary use in women with severe IBS symptoms. Both drugs have potentially serious side effects and have not been approved by the Food and Drug Administration (FDA) for treating men.

There are no surgical treatments for IBS. Some alternative therapies that some patients find helpful include acupuncture and herbal remedies, particularly peppermint tea or capsules. Peppermint is a natural antispasmodic that relaxes the intestinal muscles.


IBS is a bothersome condition but it is not life-threatening and will not cause or lead to cancer. Patients with IBS have the same life expectancy as others of their age or sex in the general population.


People with IBS cannot completely prevent occasional episodes of diarrhea or constipation with any medications presently available, but they can minimize the severity of their symptoms in a number of ways:

  • Psychotherapy or counseling. Some people find their symptoms are helped by learning to avoid overreacting to normal life stressors.
  • Getting regular exercise. Exercise helps to maintain bowel function as well as lower stress levels.
  • Avoiding foods that produce cramping or gas. These include coffee, spicy foods, beans, onions, broccoli, and cabbage.
  • Practicing eating slowly and avoiding overeating.
  • Quitting smoking and reducing or eliminating alcoholic beverages.
  • Practicing yoga, meditation, relaxation techniques, or deep breathing.
  • Cutting back on cola drinks and other carbonated beverages.
  • Adding wheat bran or other foods high in fiber to the diet.
  • Hypnosis. Some patients with IBS report significant symptom relief when they are taught self-hypnosis aimed at relaxing the muscles of the abdomen.

The Future

IBS is likely to continue to be a common problem among American adults. Current research includes clinical trials of several new drugs for IBS; investigations of alternative therapies, including traditional Chinese

medicine, St. John's wort (a herbal remedy), and massage therapy; and imaging studies to see whether the brains of patients with IBS are different from those of people without the disorder.

SEE ALSO Celiac disease; Crohn disease; Fibromyalgia; Lactose intolerance; Ulcerative colitis


Antispasmodic : A type of drug given to relieve the cramping of the intestines or other muscles.

Lactose intolerance : An inability to digest lactose, the form of sugar found in milk and milk products.

For more information


Bonci, Leslie. American Dietetic Association Guide to Better Digestion. New York: John Wiley and Sons, 2003.

Darnley, Simon, and Barbara Millar. Understanding Irritable Bowel Syndrome. Hoboken, NY: John Wiley and Sons, 2003.

Magee, Elaine. Tell Me What to Eat If I Have Irritable Bowel Syndrome. New York: Rosen Publishing Group, 2009.


American College of Gastroenterology. Understanding Irritable Bowel Syndrome. Available online in PDF format at http://www.acg.gi.org/patients/ibsrelief/IBS.pdf (updated May 8, 2003; accessed August 19, 2008).

KidsHealth. Irritable Bowel Syndrome. Available online at http://kidshealth.org/kid/health_problems/stomach/ibs.html (updated October 2007; accessed August 19, 2008).

Mayo Clinic. Irritable Bowel Syndrome. Available online at http://www.mayoclinic.com/health/irritable-bowel-syndrome/DS00106 (updated May 9, 2008; accessed August 19, 2008).

National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Irritable Bowel Syndrome. Available online at http://digestive.niddk.nih.gov/ddiseases/pubs/ibs/index.htm (updated September 2007; accessed August 19, 2008).

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